And, approaching this question, it will be well for us to bear two things in mind. In the first place, our definitions both of substance and of accident are abstract and generic or universal. But the abstract and universal does not exist _as such_. The concrete, individual, actually existing substance is never _merely_ “a being that naturally exists in itself,” nor is the accident of such a substance _merely_ a verification of its definition as “a being that naturally inheres in something else”. In every case what really and actually exists is _the individual_, a being concreted of substance and accidents, a being which is ever and always a _real unity_, composite no doubt, but really one; and this no matter what sort of distinction we hold to obtain between the substance and its accidents. This is important; its significance will be better appreciated according as we examine the distinctions in question. Secondly, as scholastics understand a real distinction, this can obtain not merely between different “persons” or “things” which are separate from one another in time or space, but also between different constitutive principles of any one single concrete, composite, individual being (38). We have seen that they are not agreed as to whether the essence and the existence of any actual creature are really distinct or not (24). And it may help us to clear up our notion of “accident” if we advert here to their discussion of the question whether or not an accident ought to be regarded as having an existence of its own, an existence proper to itself.